The ultimate goal of eradication of HIV-1 from infected persons requires the treatment with combination of drugs with different mechanisms of inhibition of the virus. The overall objectives of the project are the development of new antiviral drugs with a mechanism of inhibition of HIV-1 different from those of currently available drugs. The specific aim of this proposal is to design compounds which inhibit the binding of HIV-1 RT with Template-Primer DNA (T-P DNA), a pre-requisite step in HIV-1 replication. T-P DNA binds a highly conserved region, alpha Helix H, in which any mutation results in loss of frame-shift fidelity. Recently, a natural product 3,5,8-trihydroxy-4-quinolone (THQ), from a marine sponge, was shown to inhibit the binding of T-P DNA with HIV-1 RT. However, THQ was unstable when exposed to air. In our six-month Phase I studies we have successfully demonstrated that by careful design and synthesis we could identify compounds more active and more stable than THQ. Especially, one of the new compounds was about ten-fold more active than THQ. Its mechanism of action is similar to that of THQ in blocking the binding of HIV-1 RT with T-P DNA. It also inhibited HIV-1 in lymphocyte cell culture assays. Through Structure-Activity analysis, we have identified features that are crucial for HIV-1 inhibition. This Phase II application describes the design and synthesis of third generation compounds with these structural features which will greatly enhance their ability to inhibit HIV-1 without significant cytotoxicity. A letter from Merck & Co., expressing keen interest and willingness to assay our compounds for efficacy and toxicity for the follow-on development, is included in this proposal. These drug candidates with unique mode of inhibition of the virus are expected to be effective against HIV-1, either per se, or in combination with currently available drugs. There is an excellent commercial potential for an antiviral drug for which escape mutants are less likely due to loss of viability of the mutant strain. PROPOSED COMMERCIAL APPLICATIONS: HIV-1 strains resistant to single or multiple drugs have been isolated from patients treated with every class of drugs in clinical or experimental use. The drugs described in this application are directed against a conserved region of HIV-1 RT crucial for its binding with Template-Primer DNA, a pre-requisite step for viral replication. These drugs, because of the unique mechanism of action, will have excellent commercial potential for use in treating patients infected with HIV- 1.